Related: fdo#71147 lwp-files open not or without charts/tables

It seems pContent may be NULL (see https://bugs.freedesktop.org/attachment.cgi?id=88539)

Change-Id: I80249dd1d0afc3feaef5f1b1d134210beee3d029
Reviewed-on: https://gerrit.libreoffice.org/6536Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

lotuswordpro/source/filter/xfilter/xfframe.cxx

@@ -92,6 +92,8 @@ XFFrame::~XFFrame()
 
 void    XFFrame::Add(IXFContent *pContent)
 {
+    if (!pContent)
+        return;
     XFContentContainer::Add(pContent);
     if( pContent->GetContentType() == enumXFContentFrame )
     {